This invention claims a priority based on Japanese Patent Application No.11-239907 filed on Aug. 26, 1999, the entire contents of which are incorporated herein by reference for all purposes.
The present invention relates to a data recording and reproducing apparatus which records and reproduces data on and from a disc-shaped recording medium according to the ZCLV (zoned constant linear velocity) scheme.
In the ZCLV scheme, the recording area of a disc-shaped recording medium is divided in the radial direction into a plurality of doughnut-shaped zones and data are recorded or reproduced at a constant linear velocity in each zone. The angular velocities of the respective zones are so set that a zone closer to the outer periphery has a lower angular velocity.
The ZCLV scheme can realize a simpler rotation control than the CLV scheme in which the angular velocity varies over the entire recording area of a disc-shaped recording medium, because in the ZCLV scheme the angular velocity is constant in each zone, that is, the angular velocity varies only in a zone-by-zone basis. Further, the ZCLV scheme can make the linear recording density more even and hence enables recording of more data on a recording medium than the CAV (constant angular velocity) scheme in which the angular velocity is constant over the entire recording area of a disc-shaped recording medium, because in the ZCLV scheme the angular velocities of the respective zones are so set that a zone closer to the outer periphery has a lower angular velocity though the angular velocity is constant in each zone.
Conventionally, the DVD-RAM (digital versatile disc-random access memory) that is a rewritable optical disc is known as an example of disc-shaped recording media on and from which data are recorded and reproduced according to the ZCLV scheme.
Incidentally, Japanese Unexamined Patent Publication No. Hei. 5-234252 discloses what is called a simultaneous recording and reproducing technique for reproducing recorded data from a disc-shaped recording medium while recording data on it.
In the simultaneous recording and reproducing technique of this publication, a single recording and reproducing head is used and data that are input at a constant rate are recorded on a disc-shaped recording medium in a shorter time than the data input period. A period in which no recording is performed is produced in a data input period in this manner, and recorded data are reproduced from the disc-shaped recording medium in the period thus produced. The reproduced data are elongated in time and output at a constant rate.
Where it is attempted to apply the simultaneous recording and reproducing technique of the publication No. Hei. 5-234252 to a disc-shaped recording medium on and from which data are recorded and reproduced according to the ZCLV scheme, the following problem arises.
Now, a unit for switching data between recording and reproduction is called xe2x80x9cdata block.xe2x80x9d In the ZCLV scheme, there may occur a case that one data block is recorded in two adjacent zones. In this case, since in the simultaneous recording and reproducing technique of the above publication recording of a data block and reproduction of a recorded data block are performed alternately, during recording of a data block a first change in angular velocity occurs when the recording and reproducing head is moved from a first zone where recording of the data block is stared to a second zone. A second change in angular velocity occurs when the recording and reproducing head is returned from the second zone to the first zone to reproduce the recorded data block. Further, a third change in angular velocity occurs when the recording and reproducing head is moved from the first zone to the second zone during reproduction of the data block.
Incidentally, when the angular velocity has been changed, there is a rotation lock waiting time when neither recording nor reproduction can be performed which is a time to wait for stabilization of the new angular velocity. Therefore, if the simultaneous recording and reproducing technique of the above publication is applied to the ZCLV scheme, it may be necessary to perform rotation lock waiting three times in addition to recording and reproducing of one data block during an input and output period of the one data block. As a result, the data input and output rate in a simultaneous recording and reproducing operation is lowered by an amount corresponding to three rotation lock waiting times.
An object of the present invention is to prevent occurrence of such rotation lock waiting times and thereby increase the data input and output rate in a simultaneous recording and reproducing operation in a data recording and reproducing apparatus which records and reproduces data on and from a disc-shaped recording medium according to the ZCLV scheme.
To attain the above object, the invention provides a data recording and reproducing apparatus which performs a simultaneous recording and reproducing operation in which, in an input period of data constituting one data block, another data block that was input immediately before is recorded on a disc-shaped recording medium on which recording and reproducing are performed according to a ZCLV scheme and the recorded one data block is reproduced, comprising reproducing means for reproducing a data block; and reproduction control means for controlling the reproducing means in a simultaneous recording and reproducing operation so that the reproducing means reads a data block that has been recorded on the disc-shaped recording medium so as not to extend over two ZCLV zones from the disc-shaped recording medium for reproducing it, and does not read a data block that has been recorded on the disc-shaped recording medium so as to extend over two ZCLV zones from the disc-shaped recording medium for reproducing it.
In the invention, a data block that has been recorded in two adjacent zones is not read from the disc-shaped recording medium for reproducing. As a result, no rotation lock waiting time occurs in reproducing one data block. A rotation lock waiting time occurs only once when the data block is recorded in a zone different from a zone in which the immediately preceding data block is recorded or when the data block is recorded in two adjacent zones. Therefore, the maximum time of the sum of rotation lock waiting times occurring in a simultaneous recording and reproducing operation of one data block is reduced, by two rotation lock waiting times, than the maximum time in the conventional case that is equal to the sum of three rotation lock waiting times. The data input or output rate in a simultaneous recording and reproducing operation can be made higher than in the conventional case by an amount corresponding to two rotation lock waiting times.
In the invention, there may be provided a buffer for holding, in the simultaneous recording and reproducing operation, a data block to be recorded on the disc-shaped recording medium, and the reproduction control means may control the reproducing means in the simultaneous recording and reproducing operation so that the reproducing means reads a data block that has been recorded on the disc-shaped recording medium so as not to extend over two ZCLV zones from the disc-shaped recording medium for reproducing it and reads a data block that has been recorded on the disc-shaped recording medium so as to extend over two ZCLV zones from the buffer for reproducing it, without reading it from the disc-shaped recording medium.
This makes it possible to prevent breaks of reproduction sound that would otherwise occur in a simultaneous recording and reproducing operation because data blocks that are recorded in two adjacent zones are not reproduced from the disc-shaped recording medium.
In the invention, there may be provided position storing means for storing a position on the disc-shaped recording medium of a data block that has been recorded on the disc-shaped recording medium so as to extend over two ZCLV zones in the simultaneous recording and reproducing operation. And the reproduction control means may control the reproducing means after completion of the simultaneous recording and reproducing operation so that the reproducing means reproduces the data block recorded on the disc-shaped recording medium at the position stored in the position storing means.
This makes it possible to check, after completion of a simultaneous recording and reproducing operation, whether data blocks that were recorded on two adjacent zones were properly recorded on the disc-shaped recording medium.